The industry is pushing towards preventing pre-owned games, this would be a sweet slap of irony if the consoles themselves will retain the details of installed games allowing the new ower (in the event of selling your console) to obtain all the games you owned.

Whether this works or not depends a lot on the method used to "clear" the pre-owned console. If you use "Clear All Content and Settings" in the Settings menu to clear the console, then yes, any eShop content will still be active on the Wii U and can then theoretically be downloaded again. If the Nintendo Network ID itself was deleted (which has to be done explicitly, "Clear All Content And Settings" doesn't actually do this) via a deletion of the specific user who purchased that content, then that content cannot ever be downloaded/used again on that console without buying it once more. Similarly, content purchased on a Wii U cannot be used on another Wii U as you cannot 'sign in' to a different Wii U once your NNID has been created, thus binding your NNID seemingly permanently to the console it was created on. Hopefully this information is useful to someone.

I remember reading something like that too and I hope it does happen sometime soon. I was unlucky with my first Wii U, it was defective and I had to exchange it, so I lost the NNID I made on it and one eShop purchase. Thankfully it was only $10 worth though, it could have been a bigger loss